10 ECOLOGY AND LIFE HISTORY OF THE COMMON FROG 



however, would be a thermometer, a notebook and a pencil, and the 

 ability to recognize dead eggs, a very easy matter. 



Up to this point, the narrative has depended on work most of which 

 has already been published. This extraordinary material, the jelly of 

 the egg, has still some further surprises to yield up, and in the following 

 paragraphs I give an account of some observations not yet complete in 

 some of the biochemical and physiological aspects, but sufficiently so 

 to form a part of this ecological story. 



Biochemical Properties of the Jelly 



By a coincidence. Dr. Burgess Bamett and I shared a common 

 interest in two unrelated scientific fields — the study of amphibia and 

 of blood-clotting. In May 1939, Dr. Barnett, who had just left the 

 Zoological Society of London, where he had been the Curator of 

 Reptiles, for a similar post at Rangoon, wrote to say that he had 

 "stumbled upon" a curious property of the frog's egg. The jelly 

 contained a clotting factor which he likened to the prothrombin of 

 blood. He invited me to collaborate in its investigation, and when I 

 accepted he sent me the only notes that he had. They consisted of 

 some tests on normal and on haemophihc blood. In 1939, the subject 

 of blood-coagulation, although it already had a large hterature, had 

 not grown to the enormous extent that it has now assumed, and in the 

 hght of more recent knowledge, it is clear that the factor he had 

 discovered was not prothrombin, but a variety of thromboplastin. 

 Thromboplastins are rather widely distributed in nature, sometimes 

 occurring in unexpected places, and if this had been the only point, 

 there would have been only a mild interest in the fact. From Dr. 

 Bamett's letters it seems clear that he had not any idea of the possible 

 function of the factor, and very tentatively he suggested that it might 

 be protective. He was perhaps led to this view from his recent studies, 

 with Dr. R. G. Macfarlane (1934), on the clotting properties of the 

 venom of the Russell viper, which kills its prey by injecting a variety 

 of thromboplastin. Before we reached the point of actually collabo- 

 rating. Dr. Bamett died. There the matter remained, until in planning 

 this chapter I reahzed the probable function of the factor and the part 

 it may play in the ecology of the frog and very likely in the hves of 

 other species as well. 



It is necessary at this stage to explain very briefly the function of 

 these factors in the coagulation of the blood, for there is now httle 



